This invention relates to an improved method for reducing carbon monoxide emissions from a titanium dioxide fluidized bed chlorinator.
In such fluidized bed chlorinator, chlorine, coke, and titanium bearing material are fed to a fluidized bed under conditions which chlorinate the titanium and many other impurities. Gaseous titanium tetrachloride, other metallic chlorides such as iron chloride, carbon monoxide, carbon dioxide and other reaction products exit the fluidized bed reactor. The gaseous titanium tetrachloride produced can then be separated from the other metal chlorides and impurities and used to produce titanium dioxide pigment or titanium metal.
It would be desirable to have a simple method to reduce the amount of carbon monoxide emitted from the reactor because environmental requirements often restrict its release to a low level. While some means are known to reduce the amount of carbon monoxide emitted, they involve addition of compounds which can be undesirable in the titanium dioxide pigment or in the process to make such pigment.
The following information is disclosed which may be of interest to this invention.
U.S. Pat. No. 2,790,703 discloses a process for chlorinating titanium containing material by using carbon monoxide for the reducing agent. It is mentioned at column 1, lines 32-37, that the ratio of carbon monoxide to carbon dioxide produced depends upon reaction temperature and other reaction conditions. In Example 1, it is mentioned that the reaction products can be cooled by the addition of cold, liquid, titanium chloride.
U.S. Pat. No. 3,883,636 discloses a process for chlorinating titanium dioxide in a fluidized bed reactor. The efficiency of chlorination (as measured by the chlorine utilization or the carbon dioxide to carbon monoxide ratio of the gases produced) is improved by conducting the chlorination in the presence of compounds of chromium, lanthanum, or vanadium.
U.S. Pat. No. 3,591,333 also discloses a process for chlorinating titanium dioxide in a fluidized bed reactor. It is stated that the carbon dioxide to carbon monoxide ratio can be increased by the addition of compounds of magnesium, calcium, strontium, barium, cadmium and mixtures thereof.